| APA | HHDU. (2012, February 16). In Acronym Geek. Retrieved 01:16, February 16, 2012, from http://www.acronymgeek.com/HHDU |
| MLA | "HHDU." Acronym Geek. (2012). Acronym Geek. 16 Feb 2012 <http://www.acronymgeek.com/HHDU>. |
| MHRA | 'HHDU', Acronym Geek, 16 February 2012, <http://www.acronymgeek.com/HHDU> [accessed 16 February 2012] |
| Chicago | "HHDU", http://www.acronymgeek.com/HHDU (accessed February 16, 2012). |
| CBE/CSE | HHDU [Internet]. Acronym Geek; 2012 Feb 16 [cited 2012 Feb 16]. Available from: http://www.acronymgeek.com/HHDU. |
| Bluebook | HHDU, http://www.acronymgeek.com/HHDU (last visited February 16, 2012). |
| Bluebook: Harvard JOLT | See Acronym Geek, HHDU, http://www.acronymgeek.com/HHDU (optional description here) (as of Feb. 16, 2012, 01:16). |
| AMA | HHDU. Acronym Geek. February 16, 2012, 01:16. Available at: http://www.acronymgeek.com/HHDU. Accessed February 16, 2012, 01:16. |